Electrical Conduction Block Implant Device

ABSTRACT

The present invention provides an electrical block implant sized and shaped for securement at the perimeter of the pulmonary ostium of the left atrium. By utilizing various expandable ring designs and optional anchoring mechanisms, the present invention causes even, circular scarring around the perimeter of the pulmonary ostium, achieving reliable blocking of aberrant electrical signals responsible for atrial fibrillation.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/792,110 filed Mar. 2, 2004 entitled Electrical Conduction BlockImplant Device, which claims priority to U.S. Provisional ApplicationSer. No. 60/451,865 filed Mar. 3, 2003 entitled Implantable Device toCreate Ostial Electrical Block in the Pulmonary Veins for Treatment ofAtrial Fibrillation and to U.S. Provisional Application Ser. No.60/451,864 filed Mar. 3, 2003 entitled Implantable Ring to CreateElectrical Block in Pulmonary Vein Ostium for Treating AtrialFibrillation, the entire contents of all of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

Pumping of the human heart is caused by precisely timed cycles ofcompartmental contractions of the heart muscle which lead to anefficient movement of blood into the heart and out to the various bodilyorgans. These precisely timed cycles are controlled and directed byelectrical signals that are conducted through the cardiac tissue and canbe referred to as pacing signals.

The sinoatrial node (SA node) is the heart's natural pacemaker, locatedin the upper wall of the right atrium. The SA node spontaneouslycontracts and generates nerve impulses that travel throughout the heartwall causing both the left and right atriums to sequentially contractaccording to a normal rhythm for pumping of the heart. These electricalimpulses continue to the atrioventricular node (AV node) and down agroup of specialized fibers called the His-Purkinje system to theventricles. This electrical pathway must be exactly followed for properfunctioning of the heart.

When the normal sequence of electrical impulses changes or is disrupted,the heart rhythm often becomes abnormal. This condition is generallyreferred to as an arrhythmia and can take the form of such arrhythmiasas tachycardias (abnormally fast heart rate), bradycardias (abnormallyslow heart rate) and fibrillations (irregular heart beats).

Of these abnormal heart rhythms, fibrillations, and particularly atrialfibrillations, are gaining more and more attention by clinicians andhealth workers. Atrial fibrillation develops when a disturbance in theelectrical signals causes the two upper atrial chambers of the heart toquiver instead of pump properly. When this happens, the heart is unableto discharge all of the blood from the heart's chambers thus creating asituation where the blood may begin to pool and even clot inside theatrium. Such clotting can be very serious insofar as the clot can breakaway from the atrial chamber and block an artery in the brain, andthereby cause a stroke in the individual.

A variety of treatments have been developed over the years to treatatrial fibrillation, namely, treatments to either mitigate or eliminateelectrical conduction pathways that lead to the arrhythmia. Thosetreatments include medication, electrical stimulation, surgicalprocedures and ablation techniques. In this regard, typicalpharmacological treatments have been previously disclosed in U.S. Pat.No. 4,673,563 to Berne et al.; U.S. Pat. No. 4,569,801 to Molloy et al.;and also by Hindricks, et al. in “Current Management of Arrhythmias”(1991), the contents of which are herein incorporated by reference.

Surgical procedures, such as the “maze procedure”, have also beenproposed as alternative treatment methods. The “maze” procedure attemptsto relieve atrial arrhythmia by restoring effective atrial systole andsinus node control through a series of incisions.

The Maze procedure is an open heart surgical procedure in whichincisions are made in both the left and right atrial walls whichsurround the pulmonary vein ostia and which leave a “maze-like” pathwaybetween the sinoatrial node and the atrioventricular node. The incisionsare sewn back together but result in a scar line which acts as a barrierto electrical conduction.

Although the “maze” procedure has its advantages, in practice it can bea complicated and a particularly risky procedure to perform since thesurgeon is making numerous physical incisions in the heart tissue. Duein part to the risky nature of the Maze procedure, alternative,catheter-based treatments have been advanced. Many of these catheterdevices create the desired electrical block by way of ablation devicesdesigned to burn lesions into the target tissue. Examples of thesedevices can be seen in U.S. patents: U.S. Pat. No. 6,254,599 to Lesh;U.S. Pat. No. 5,617,854 to Munsif; U.S. Pat. No. 4,898,591 to Jang etal.; U.S. Pat. No. 5,487,385 to Avitall; and U.S. Pat. No. 5,582,609 toSwanson, all incorporated herein by reference.

Although ablation catheter procedures remain less invasive than previoussurgical methods like the “maze” procedure, they nevertheless retain asignificant element of risk. For example, ablation procedures oftenutilize high power RF energy or ultrasonic energy, which may adequatelycreate electrical block, but their inherent destructive nature allowsfor the possibility of unintended damage to the target tissue or nearbyareas.

Further, it is often difficult to achieve certainty as to whether theappropriate amount of ablation has been performed uniformly around theperimeter of the target site or if the desired site is even beingablated.

Ablation procedures have also seen an occurrence of stenosis in thepulmonary veins as a response to the ablation. This is a seriouscomplication and as a result, many doctors try to limit their treatmentto the ostium of the pulmonary veins to minimize the risk of creating astenosis in the pulmonary veins.

Finally, various implant devices have also been proposed. Examples ofsuch proposed devices are disclosed in co-pending U.S. application Ser.No. 10/192,402 filed Jul. 8, 2002 entitled Anti-Arrhythmia Devices andMethods of Use, the entire contents of which is hereby incorporated byreference.

The solutions in the prior art, however, are not believed to be entirelyeffective in many cases, and indeed may result in actually inducing longterm arrhythmias and inefficacy.

As a result, what is needed are minimally invasive techniques forcreating electrical block in the pulmonary veins which reduce thecomplication risk of previously known procedures, while increasingeffectiveness and speed of the procedure to create electrical block.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a minimally invasivedevice and technique for deploying such a device that safely andeffectively blocks aberrant electrical signals at or near the ostium ofthe pulmonary veins.

It is a further object of the present invention to provide a minimallyinvasive electrical block device that is easy to deploy and has a lowrisk of complication.

It is yet a further object of the present invention to provide anelectrical block device that consistently creates a circumferential scarline around the pulmonary ostium to completely block aberrant electricalsignals causing atrial fibrillation.

The present invention achieves these objects by providing an electricalblock implant sized and shaped for securement at the perimeter of thepulmonary ostium of the left atrium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A-1C illustrate three example variations of pulmonary ostia;

FIG. 2 illustrates a flattened sectional view of an expandable ringaccording to the present invention;

FIG. 3 illustrates a side view of an electrical block device accordingto the present invention;

FIG. 4 illustrates the electrical block device of FIG. 3 at a pulmonaryvein bifurcation;

FIG. 5 illustrates the electrical block device of FIG. 3 in an expandedposition;

FIG. 6 illustrates the electrical block device of FIG. 3 in a fullydeployed position;

FIG. 7 illustrates the electrical block device of FIG. 3 in a fullydeployed position;

FIG. 8 illustrates a side view of an electrical block device accordingto the present invention;

FIG. 9 illustrates a side view of an electrical block device accordingto the present invention;

FIG. 10 illustrates a side view of an electrical block device accordingto the present invention;

FIG. 11 illustrates a side view of an electrical block device accordingto the present invention;

FIG. 11A illustrates a side view of an electrical block device accordingto the present invention;

FIG. 12 illustrates a side view of an electrical block device accordingto the present invention;

FIG. 13 illustrates a side view of an electrical block device accordingto the present invention;

FIG. 14 illustrates a side view of an expandable ring according to thepresent invention;

FIG. 15 illustrates a partial close up side view of an expandable ringaccording to the present invention;

FIG. 16 illustrates a flattened sectional view of the expandable ring ofFIG. 14;

FIGS. 17A and 17B illustrate cross-sectional views of a conduction blockdevice of the present invention in its implanted state;

FIG. 18 illustrates another embodiment of the expandable ring designaccording to the present invention;

FIG. 19 illustrates another embodiment of the expandable ring designaccording to the present invention;

FIG. 20 illustrates a side view of an electrical block device accordingto the present invention;

FIG. 21 illustrates a flattened sectional view of a primary expandablering of FIG. 20;

FIG. 22 illustrates a top view of a secondary pressure ring according tothe present invention;

FIG. 23 illustrates a top view of a secondary pressure ring according tothe present invention

FIG. 24 illustrates a side view of an expandable ring according to thepresent invention;

FIG. 24A illustrates a flattened sectional view of the expandable ringof FIG. 24;

FIG. 25 illustrates a side sectional view of an expandable ringaccording to the present invention;

FIG. 26 illustrates a side sectional view of an expandable ringaccording to the present invention;

FIG. 27 illustrates a flattened sectional view of the expandable ring ofFIG. 26;

FIGS. 28A-28C illustrate a preferred embodiment of a delivery system inaccordance with the present invention;

FIGS. 29A-29C illustrate another preferred embodiment of a deliverysystem in accordance with the present invention;

FIG. 30 illustrates another preferred embodiment of a delivery system inaccordance with the present invention;

FIG. 31 illustrates another preferred embodiment of a delivery system inaccordance with the present invention;

FIG. 32 illustrates another preferred embodiment of a delivery system inaccordance with the present invention;

FIG. 33 illustrates another preferred embodiment of a delivery system inaccordance with the present invention;

FIG. 34 illustrates a side view of an expandable ring according to thepresent invention;

FIG. 35 illustrates a side view of an expandable ring according to thepresent invention;

FIG. 36 illustrates a side view of a deployment apparatus according tothe present invention;

FIG. 37 illustrates a side perspective view of an electrical blockdevice according to the present invention;

FIG. 38 illustrates a side view of the electrical block device of FIG.35;

FIG. 39 illustrates a magnified perspective view of the expandable ringof FIG. 35;

FIG. 40 illustrates a side view of the electrical block device of FIG.35 in a loaded state;

FIG. 41 illustrates a side perspective view of the electrical blockdevice of FIG. 35;

FIG. 42 illustrates a top view of the expandable ring of FIG. 35 in anexpanded state;

FIG. 43 illustrates a top view of the expandable ring of FIG. 42 in acinched state;

FIG. 44 illustrates a side perspective view of the electrical blockdevice of FIG. 35; and,

FIG. 45 illustrates a top view of the electrical block device of FIG.35.

DETAILED DESCRIPTION OF THE INVENTION

The ostium of the pulmonary veins has a highly variable geometry fromone patient to another and this presents difficulty in reliably treatingatrial arrhythmias using previous methods. That is, the variablegeometry has in the past made it difficult to reliably create acontinuous line of electrical block around the perimeter of the ostiumin each and every patient.

In illustration of this point, FIGS. 1A-1C present three ostiumgeometries that can occur in the general human population. These Figuresshow a left atrium 10 of a human heart wherein two adjacent pulmonaryveins 11 may originate directly from two ostia in the left atrium (FIG.1B) or may originate from one ostia in the left atrium followed by abifurcation 13 downstream of the left atrium. Moreover, the bifurcation13 may be located near the left atrium (FIG. 1A) or far from the leftatrium (FIG. 1C). Finally, various hybrids of these geometries are alsopossible as some people can have more or less than the typical twopulmonary veins originating on each of the right and left sides of theleft atrium 10.

In addition to these geometric variations, the ostia may differ indiameter and location of the side branches from patient to patient. Forexample, typical target site diameters may range anywhere from about 10to 30 mm. This provides a considerable challenge for any consistentlyperformed electrical block procedure for the treatment of an atrialarrhythmia.

To address this problem, the present invention provides an electricalblock device that is implantable and anchorable within the pulmonaryveins and/or left atrium of many different geometries. That is, thepresent invention presents a device and method that is adaptable for usein conducting substantially uniform treatment of a wide segment of thehuman population.

And generally speaking, the present invention performs this function ina way that consistently circumferentially blocks aberrant electricalsignals through its presence in the ostium of the pulmonary veins. Theelectrical block device in accordance with the present invention may actthrough the mere presence in the ostium and/or through controlledscarring caused by the device.

The controlled scarring can be created by a number of possiblemechanisms. One possible mechanism is to have the device press againstthe tissue with enough force to cause pressure necrosis. As the tissuenecroses, the device slowly migrates through the wall and scar tissueforms behind the device as it slowly migrates through the tissue wall.With this mechanism, it is possible that the device can ultimatelymigrate through the entire tissue wall leaving a line of scar throughthe entire wall thickness.

In another possible mechanism, the device can press against the tissuecausing tension in the tissue wall. This tension in the tissue can causefibrosis in the wall without having the device actually pass through thewall as was described for the pressure necrosis mechanism above.

Another possible mechanism is to have the presence of the device causenecrosis in the tissue as a result of a reaction to the material of thedevice or a material attached to the device. It is also possible to usecombinations of these mechanisms.

The controlled scarring is believed to disrupt the cellular structure ofcardiac tissue that is present in or on the pulmonary vein wall or theatrial wall outside the ostia and thereby prevent such cardiac tissuefrom propagating aberrant electrical signals that cause the atrialarrhythmias. While this invention describes use for electrical isolationof pulmonary veins, these same devices and methods can also be appliedto other sites such as the superior vena cava or the coronary sinus.

Electrical Block Device with Anchoring Clip

A first preferred embodiment of the present invention is depicted inFIGS. 2-7 and comprises an electrical block device 100 that has threemain functional components: an expandable ring 102, and an anchoringclip 106 and a clip loop 104 that connects the ring 102 with the clip106.

With reference to FIGS. 6 and 7, it can be seen that in the fullydeployed condition of the device 100 in an ostium 118 of a bifurcatedpulmonary vein of the heart, the expandable ring 102 expands against theostial tissue and the anchoring clip 106 abuts against the bifurcation116 of the pulmonary veins 114. It can also be seen that the anchoringclip 106 is connected to the expandable ring 102 by the clip loop 104that arcs over the diameter of the expandable ring 102.

The expandable ring 102 expands from its undeployed configuration by asmuch as 10 times or more beyond its size in a compressed state so as topress around the perimeter of the ostium. This expansile force assistsin securing the expandable ring 102 in proper position.

In addition to its function of spatially positioning the device 100 inthe ostial space, the expandable ring 102 also serves as the primarymechanism of creating the desired electrical conduction block. Theexpandable ring 102 can cause this electrical block either by inducingcontrolled scarring of the tissue contacted by the ring 102 or by themere presence of the ring itself, or by a combination of the two. And asto the use of controlled scarring, any controlled method of scarring maybe used, such as chemical coatings on the ring 102 that cause scarring,physical scarring devices mounted on the ring 102, or even mere physicalexpanding pressure from the ring 102 against the tissue.

Referring to FIG. 2, the electrical block device 100 is shown in a cutand flattened sheet configuration for illustrative purposes. As isevident, the expandable ring 102 is structured from a continuous andregularly angled wire that forms an overall wave-like or sinusoidalshape. Two ends of the clip loop 104 extend from the expandable ring 102portion of the device 100 and terminate in the wire structure that formsthe anchoring clip 106.

Preferably, the wire that forms the electrical block device 100 iscomposed of nitinol or a similar elastic metal and is formed by heatsetting to a fully expanded shape. Typically, this heat setting can beperformed in an oven or salt bath, and yields a ring that is larger inits formed diameter than the target ostium diameter. As a result, thering 102 exerts an outward force against the ostial wall when deployed,holding the device 100 in contact with the tissue.

The force exerted by the expandable ring 102 can be adjusted to adesired level by varying the thickness or width of the ring 102. Thediameter/expansion ratio of the expandable ring 102 can also be variedto yield a different profile of force applied to the tissue uponexpansion of the ring. Generally, increased expansion pressure bettersecures the expandable ring 102 in place and may further create moreprominent scarring at the target area.

In one preferred embodiment, the ring can be cut from a Nitinol tubehaving a diameter of about 0.150 inches and a wall thickness of about0.015 inches. The struts of the ring can be cut about 0.015 inches wideand with a length between turnarounds of about 0.3 inches. For a targetostia having an internal diameter of 16 mm, this ring could be cut withsix cells (i.e., it could have six turnarounds on both the top and thebottom). For this 16 mm target site, the ring could be formed to adiameter of about 20 mm. It should be noted that these dimensions aremerely exemplary and that these dimensions can vary.

As discussed above, the clip loop 104 arcs over the diameter of theexpandable ring 102 when the device is deployed. As a result, as shownin FIGS. 6 and 7, the clip loop 104 serves to position the anchoringclip 106 at an appropriate distance from the expandable ring 102, andurge the anchoring clip 106 against the bifurcation 116 between thebranches of the pulmonary vein. The curved design of clip loop 104provides for some flexibility and “springiness” between the anchoringclip 106 and the expandable ring 102.

Referring to FIGS. 2 and 5, the anchoring clip 106 of the presentpreferred embodiment provides two closely spaced loops 103, having asingle barb 105 within each of the loops 103. When a small portion oftissue of the bifurcation 116 moves between the two loops 103, the barbs105 penetrate into the tissue and thereby retain the tissue between thetwo loops 103. Any type of clip or anchoring design may be used in placeof the present anchoring clip 106 design, so long as the anchoringdevice can provide securing force from the expandable ring 102 to thetissue.

With regard to delivery of the electrical block device 100 to the targetsite, the electrical block device 100 is first compressed into anundeployed state and is placed within a deployment sheath 108, as seenin FIG. 3. Within the deployment sheath 108 is a guiding catheter 112,used for positioning and deploying the electrical block device 100. Theelectrical block device 100 sits over the guiding catheter 112 such thatthe clip loop 104 is positioned between two guide wires 110 that extendout from the distal tip of the guiding catheter 112.

The guidewires 110 are conventional steerable guidewires havingdiameters typically in the range of 0.014 inches to 0.038 inches andmust be steered down the two lumens past the bifurcation. Initially, thesheath 108 encapsulates the entire electrical block device 100 againstthe guiding catheter 112. However, as will be evident from thedescription below, this positioning configuration allows the electricblock device 100 to easily slide off of the guiding catheter 112.

Referring to FIGS. 3 and 4, the loaded sheath 108 is advanced into theatrium, where the sheath is then partially retracted (or the guidecatheter 112 is advanced out of the sheath 108) so that the clip loop104 protrudes beyond the deployment sheath 108, thereby allowing theguide wires 110 to be more easily manipulated and positioned.

As the deployment sheath 108, guiding catheter 112, and electrical blockdevice 100 are urged towards the pulmonary vein ostia, each guide wire110 travels down a different pulmonary vein, centering the anchoringclip 106 on the bifurcation 116 of the pulmonary veins. The closer theguiding catheter 112 comes to the bifurcation 116, the more preciselyaligned the anchoring clip 106 becomes with the bifurcation 116 untilthe anchoring clip 106 touches and finally “clips” onto the tissue ofthe bifurcation 116 via the barbs 105 located on the loops 103 of theclip 106.

The deployment process continues by simply sliding the deployment sheath108 back past the expandable ring 102 as is best seen in FIG. 5. Withoutthe containment of the deployment sheath 108, the expandable ring 102increases in diameter to its formed size, pressing on the target tissue.

With the electrical block device 100 secured, the guiding catheter 112and deployment sheath 108 are backed out of the atrium and removed fromthe body, leaving the device 100 in its target location as seen in FIGS.6 and 7.

Due to the variation in geometry of pulmonary ostia, a pre-operationprocedure such as MRI may be helpful to determine the geometry andapproximate diameter of the target ostium. With this information, theelectrical block device 100 may be better adjusted to suit the patient'starget ostium by adjusting aspects such as the expanded diameter of theexpandable ring 102, the length of the clip loop 104, or the size ofanchoring clip 106.

Electrical Block Device with Anchoring Barbs

The previously described preferred embodiment positioned and secured theanchoring clip 106 before securing the expandable ring 102. However, thereverse order is also possible according to a preferred embodiment shownin FIG. 8.

The preferred embodiment as shown FIG. 8 is generally similar to theprevious embodiment, with perhaps two main exceptions. In the embodimentas shown in FIG. 8, the first primary difference is the use ofpositioning barbs 220 with the expandable ring 202 and the secondprimary difference is the use of a clip loop 204 that is elastic.

The barbs 220 are located around the perimeter of expandable ring 202,providing additional anchoring support when the expandable ring 202 isin the fully expanded position. The elastic clip loop 204 secures oneither side of the expandable ring 202, in the same manner as theprevious embodiments. However, a portion of each side of the elasticclip loop 204 has a multi-angled, wave-like elastic section 205. Thiselastic section 205 allows for a degree of variation in the distancebetween the position of the deployed expandable ring 202 and thebifurcation 216.

In operation, the electrical block device 200 with anchoring barbs 220is loaded and deployed in a manner similar to the previously describedembodiment. The expandable ring 202 is loaded within a deployment sheath208 and around a guiding catheter, with the elastic clip loop 204 to sitbetween guide wires 210.

The electrical block device 200 is positioned near the desired targettissue of the ostia and the guide wires 210 are inserted into eachpulmonary vein 214. When a desired target location has been achieved,the deployment sheath 208 is withdrawn so as to expose the expandablering 202. The expandable ring 202 now being unconstrained, it expandsand presses against the target tissue, pushing barbs 220 into theperimeter of the ostium 218.

Finally, the anchoring clip 206 is secured to the bifurcation 216 usingguiding catheter 212 to apply pressure on the elastic clip loop 204towards the bifurcation 216. This elastic section 205 enables theelastic clip loop 204 to stretch in response to the pressure and thusallows the anchoring clip 206 to secure to the bifurcation 216. At thatpoint, the guiding catheter 212 and deployment sheath 208 may be removedfrom the patient.

In this manner, the electrical block device 200 with anchoring barbs 200220 provides the additional anchoring of barbs 220 while allowing for analternative method of deployment. It should be understood that althoughthis preferred embodiment allows the anchoring clip 206 to be clipped tothe bifurcation 216 after expansion of the expandable ring 202, thisorder is not the only method of deployment. The electrical block device200 with anchoring barbs 200 220 may also be deployed in a similarfashion as electrical block device 100 of the first embodiment, asdescribed above, where the anchoring clip 206 is clipped to thebifurcation 216 first, followed by deployment of the expandable ring202.

Electrical Block Device without Sheath

FIG. 9 illustrates yet another preferred embodiment of the presentinvention. In this embodiment, the overall design of the electricalblock device 300 is similar to the previously described embodiments;however, instead of utilizing a deployment sheath, a deployment wire 322is used.

More specifically, as in previous embodiments, the electrical blockdevice 300 is loaded on a guiding catheter 312 for desired positioningnear the perimeter of the ostium. A clip loop 304 is positioned betweentwo guide wires 310 at the tip of guiding catheter 312.

The main distinction of this design lies in the expandable ring 302,which, unlike previous embodiments, has a series of holes 320 integratedinto the expandable ring 302 structure. As seen in FIG. 9, a thin wire322 passes through these holes 320 in a circular path and further passesthrough a catheter wire passage 324 within the guiding catheter 312,forming a large loop. The free ends of the thin wire 322 are found onthe end opposite of the electrical block device 300 of the guidingcatheter 312. Such a design allows the tension of wire 322 to controlthe expansion state of the expandable ring 302.

The overall operation of this electrical block device 300 is similar tothe previously mentioned embodiments above. The user positions theguiding catheter 312 near the bifurcation 316 of the pulmonary veins,then attaches the anchoring clip 306 using the guide wires 310 to assistin proper positioning. Next, the user manipulates the thin wire 322 torelieve the compression of expandable ring 302, allowing the ring 302 toexpand to its full diameter, pressing against the target tissue.

To remove the wire 322 from the electrical block device 300, a usersimply pulls one end of the wire 322 until the opposite end is free ofboth the electrical block device 300 and the guiding catheter 312. Atthis point, the electrical block device 300 and the guiding catheter 312are no longer connected, so the user may remove the guiding catheterfrom the patient, allowing the electrical block device 300 to functionas intended.

This technique of controlling the deployment of the blocking device witha tether wire is shown here for a bifurcated ostium. It is anticipatedthat this same technique can be applied for other ostial geometries aswill be described below.

Alternative Electrical Block Device Designs

It should be understood that variations on the above describedelectrical block devices are possible and even desired, depending on anumber of factors such as the geometric layout of the ostium of thepulmonary veins. Five variations may be seen in the preferredembodiments of FIGS. 10-13. Consistent with the previous embodiments,these alternative embodiments similarly employ an anchoring structureand an expandable ring structure.

Referring to FIG. 10, an electrical block device 400 is comprised of anexpandable ring 402. Unlike previously described expandable rings, thisexpandable ring 402 has an overall warped structure, lending itself toplacement analogous to a saddle over a bifurcation in a pulmonaryostium. In one variation, the expandable ring 402 includes anchoringbarbs 403 to assist in securing the expandable ring 402 in place. Inanother embodiment (not shown), the anchoring barbs 403 may be absentand the expandable ring 402 is secured in place according to theexpansion force of the ring 402 (based at least in part on the size andthickness of the ring 402) against the surrounding tissue.

In this embodiment, the expandable ring 402 has a wave-like structuresimilar to previously described embodiments, yet its overallconformation curves upward at the outer sides of the pulmonary veinswhile the inner portion warps downward toward the left atrium. Thisoverall bent configuration allows the electrical block device 400 towedge into place at the ostium of the pulmonary veins.

Referring to FIG. 11, an electrical block device 404 is shown to have anexpandable wire ring 408 and an expandable vein anchor 406. The wirering 408 is an incomplete, non-continuous circle, formed to a diameterlarger than the target pulmonary ostium which allows the wire ring 408to self-expand against the target tissue.

The expandable vein anchor 406 has a circular wave-like (sinusoidal)structure which seats in a branch of the pulmonary vein just past thebifurcation and is connected to the expandable wire ring 408 with atleast one wire. The vein anchor 406 has a similar structure to wave-likeexpandable rings described in previous embodiments. Functionallyspeaking, the vein anchor 406 expands in diameter against the pulmonaryvein tissue providing additional anchoring force to secure theelectrical block device 404 to the target position.

A variation of the embodiment in FIG. 11 is shown in FIG. 11A. Thisembodiment of an electrical conduction block device 700 uses a similarexpandable wire ring 702 and an expandable vein anchor 704 connected bya connecting wire 706. However, the expandable vein anchor 704 in thisembodiment is helical as shown in FIG. 11A.

FIG. 12 illustrates yet another preferred embodiment of an electricalblock device 410, this embodiment having an expandable ring 412 and dualring anchors 414. As with previous embodiments, the expandable ring 412is formed to have a diameter larger than the target ostium diameter, andis designed for seating close to the pulmonary ostium.

Each of the dual vein anchors 414 seats within a branch of the pulmonaryvein, just past the bifurcation, and self expands to a diameter largerthan the target diameter of the pulmonary vein and thereby is securedagainst the pulmonary vein tissue. Wire supports 411 connect the dualvein anchors 414 to the expandable ring 412 and thereby secure theelectrical block device 410 in place.

Turning now to FIG. 13, yet another preferred embodiment of anelectrical block device 416 is illustrated. Although this embodimentalso is usable with many ostial geometries, it is especially useful withpulmonary ostium having no bifurcation, as seen in FIG. 13. Further,multiple electrical block devices 416 can be used for each patient,typically using one electrical block device for each pulmonary vein toprovide complete electrical isolation between the left atrium and thepulmonary veins.

In this embodiment, the electrical block device 416 has an outerexpandable ring 420 and an inner expandable ring 418. Both rings 420,418 are secured together by wire support 422. The inner expandable ring418 seats within a pulmonary vein, pressing outwardly against the veintissue while the outer expandable ring 420 seats around the opening ofthe pulmonary vein. This embodiment allows the two rings to have eithercommon or different functions. They can both be used to generatescarring as described above. They can also be configured such that theinner expandable ring 418 acts primarily as an anchoring/positioningring and thereby allows outer expandable ring 420 to be held against thetissue around the ostium and to thereby serve as the scar generatingring.

Both rings 418, 420 have an angular wave-like design, allowing forcompression in diameter during the pre-deployment phase andself-expansion during the deployment phase. In this fashion, electricblock device 416 provides an alternative design for varying pulmonarygeometries.

Electrical Block Device Coatings

The electrical block devices of the present invention as disclosedherein may be coated with a variety of chemicals or drugs to furtherenhance functionality. Such coatings may include drugs, chemicals,proteins, or other materials.

In one preferred embodiment of the present invention, portions of theelectrical block device are coated with stenosis inhibiting drugs suchas rapamycin or pacitaxel, as described in patents U.S. Pat. Nos.6,273,913 and 6,231,600, the contents of which are hereby incorporatedby reference.

The portions of the electrical block device which extend into thepulmonary vein may be of the most interest to coat, so as to limit therisk of pulmonary vein stenosis caused by the anchoring component of theimplant yet not impacting the scarring response to the expandable ringdesired in the ostium.

In another preferred embodiment, portions of the electrical block deviceare coated with a polymer material such as urethane or polyester, inorder to promote the desired scarring around the ring while theanchoring components could remain uncoated or have a stenosis inhibitingcoating as described above. Such a polymer coating could also bebio-absorbable, allowing for partial integration into the target tissuearea.

In a further preferred embodiment, the expandable ring has ascar-inducing coating for enhancing the electrical blocking scarformation created by the expandable ring. Such coatings may includepolymers, bioabsorbable polymers, platings (e.g., copper), polymersloaded with drugs (e.g., tetracycline), or drugs alone.

Expandable Ring Variations

Although the expandable electrical conduction block device of thepresent invention has been described in previous embodiments asprimarily relying on a single zigzagging ring, it should be understoodthat a number of more complex variations are possible. Each variationmay have different advantages beneficial to different pulmonary ostiageometries.

In a preferred embodiment seen in FIGS. 14-16, an expandable electricalconduction block device 500 is illustrated having a primary ring 504 (orprimary “cell”) and a secondary ring 502 (or secondary “cell”), formedfrom a single piece of material. As with previously described conductionblock devices, this design may be compressed to a smaller size forloading into a deployment sheath or other deployment device so that itexpands to a large diameter when free of such deployment devices. FIGS.14 and 15 shows the conduction block device 500 in an expanded statewhile FIG. 16 shows a sliced and flattened section of the device 500 inan unexpanded state.

The electrical conduction block device 500 has a primary ring 504connected to a secondary ring 502 at the angled bend points or strutconnection points of each ring. The primary ring 504 has a wider strutthan the secondary ring 502, increasing the stiffness of the primaryring 504, while the secondary ring 502 is shorter in circumference thanthe primary ring 504. The differing circumferences of each ring allowsfor an expanded shape seen in FIG. 14, with the secondary ring 502 fullyextended to an essentially unbent circle and primary ring 504 extendedto an overall wavy/sinusoidal shape. In a preferred embodiment,anchoring barbs 506 are present at the angled bend points of primaryring 504, providing additional anchoring force to maintain the targetposition of the electrical block device.

This two-ringed or two-cell design has a number of advantages, one ofwhich is increased force per area on the target tissue by the secondaryring 502 relative to the primary ring 504. In this regard, the radialforce exerted by the device against the wall of the target vessel isdriven in large part by the width of the ring material. In other words,a wider ring can expand with more force than a thinner ring. A tissuenecrosis mechanism for creating scars is a function of the pressure(force per unit area) exerted by the electrical block device against thetarget tissue. Since the primary ring 504 is wider than the secondaryring 502 and the two rings are connected together (allowing some of theradial expansion force generated by the primary ring 504 to be appliedto the tissue contacted by the secondary ring 502), the secondary ring502 thus causes a greater amount of force per area as between the two.As a result, the secondary ring 502 can be designed to create a desiredscar line while the primary ring 504 can be designed to provide theprimary anchoring function.

In this regard, FIGS. 17A and 17B provide a cross-sectional view of howthe secondary ring 502 causes the scarring response. FIG. 17A shows theplacement of the conduction block device 500 immediately after placementof the device 500 at the target site. As is evident, the barbs 506 haveinitially engaged the tissue wall but there is not yet any migration ofthe device into the tissue wall nor any scar line.

FIG. 17B, on the other hand, shows the configuration of the conductionblock device 500 after migration has occurred. As is evident in thisembodiment, the greater force per area of the secondary ring 502 hascaused the barbs 506 on the top end of the secondary ring 502 to extendinto and even break through the tissue wall whereas the barbs 506 at thelower end of the primary ring 504 remain embedded in the tissue wallthickness. As is also evident, this migration has caused the creation ofa scar line (indicated by the shaded area 503), including a scar line503 that traverses the entire thickness of the tissue wall and encasesor encapsulates the barb 506 of the secondary ring 502 that has extendedthrough the tissue wall.

Another advantage to the dual ring design of the expandable ring 500 isthat the secondary ring 502 is stretched into a nearly straight circlethereby allowing the secondary ring 502 to inscribe a substantiallystraight scar line around the internal circumference of the pulmonaryvein. That is, the substantially straight scar line created by thesecondary ring 502 avoids forming a scar line that extends axiallyupstream in the vein (away from the atrium) as would be the case if thesecondary ring 502 was configured to have a wave-like shape in thedeployed state.

This is important insofar as the electrical sources that must beisolated from the atrium in treating atrial arrhythmias are suspected toreside in close proximity to the ostium. These sources may be missed orinadequately isolated if the scar line, or a portion of the scar line,is created too far upstream in the vein (away from the atrium).Additionally, as discussed previously, the anatomy around the ostiumoften includes side branches or curves which make it more difficult tocreate a full circumferential scar line with a wave-like ring.

Finally, the electrical block device 500 that uses two rings (or“cells”) in this manner allows the formation of a discrete, narrow scarline yet has the positional stability of an axially extensive implant.In other words, the use of two rings 502, 504 in this manner leads to anarrow scar line around the ostium and also provides sufficient axiallength so as to better ensure proper deployment and retention at thesite. This is important as it is known that implants that have anincreased ratio of diameter to axial length are more prone to misdeployor “tumble” during deployment.

In a preferred embodiment of the expandable ring 500, the primary ring504 and the secondary ring 502 are cut from a single tube of memoryelastic metal, such as nitinol as shown in FIG. 16. Each ring 502, 504of the tubular structure is then stretched over a larger diameter ringand heat set in a furnace at about 540 degrees Celsius. The final formeddiameter of each should allow the secondary ring 502 to stretch out toalmost a straight circle as shown in FIGS. 14 and 15. The formeddiameter of the expandable ring 500 is preferably larger in diameterthan the target vessel by 5-100%, and more preferably by about 15% to40%.

Electro-polishing components of the expandable ring 500 may be necessaryto prevent micro surface cracks from propagating when the device isstrained in forming. These cracks can cause the device to fracture andmust be eliminated by polishing before applying high strain to thecomponents. Nitinol components of the expandable ring 500 can beelectro-polished using percloric acid, nitric acid, or other compoundsknown to one skilled in the art. It may be desirable to form the deviceto a higher diameter in which case electro-polishing in stages may benecessary. This results from the fact that some expansion may be neededbefore being able to polish uniformly and from the fact that polishingmay need to precede final expansion.

FIGS. 18 and 19 show two possible other formed geometries for theconduction block device 500 described with reference to FIG. 16. FIGS.18 and 19 show the end of the device 500 with the secondary ring 502being formed to a larger diameter than the end of the primary ring 504without the secondary ring 502. As described earlier, the ratio of thediameter of the formed device to the diameter of the target site for theimplant is an important driver of the magnitude of the radial forceexerted by the device against the tissue of the target site. By formingthe device tapered as in FIG. 18 or flared as in FIG. 19, it is possibleto produce higher pressures against the tissue under the secondary ring502 than under most if not all of the primary ring 504. This isindependent of the pressure differences resulting from the widthdifferences between the two rings as described previously. The result ofthis configuration is to have the secondary ring 502 apply enoughpressure against the tissue wall to migrate through the wall due topressure necrosis while most, if not all, of the primary ring 504applies less pressure against the tissue so that it secures the positionof the device 500 while creating reduced necrosis or fibrosis or, insome cases, perhaps no necrosis or fibrosis.

Referring to FIGS. 20-22, another embodiment of an electrical blockdevice 511 is shown. As with the embodiment of FIGS. 14-16, thiselectrical block device 511 includes a primary ring 508 and a secondaryring 514. However, each ring 508, 514 is formed separately and laterassembled to create the electrical block device 511 as discussed below.

The primary ring 508 has a wave shape in its expanded form as shown inFIG. 20. It is formed from a tube with the cut path around thecircumference of the tube shown in FIG. 21. It includes barbed securingspikes 510 and anchoring spikes 512, as also is seen in FIG. 18. Thesesecuring spikes 510 are sized to fit within spike apertures 515 that aredisposed on the secondary ring 514 which is depicted in FIG. 22. Thus,by inserting the barbed securing spikes 510 of the primary ring 508 intothe spike apertures 515 of the secondary ring 514, the unitaryelectrical block device 511 is formed. The assembled device 511 may thenbe compressed and expanded as needed for loading and deployment asdiscussed with previous embodiments. This embodiment allows thesecondary ring 514 to project radially out further than the primary ring508 as shown in FIG. 20. This can aid in focusing the pressure againstthe tissue to the areas contacted by secondary ring 514.

Referring to FIG. 23, an alternate preferred embodiment may comprise asecondary ring 516 that functions as described with previous embodimentsbut that further includes a plurality of points 519 arranged around itsouter edge. These points provide additional anchoring force, as well asadditional scarring capability for the secondary ring 516.

Referring to FIG. 24 and FIG. 24A, another preferred embodiment of anelectrical block device 535 is contemplated wherein the primary ring 536has struts 537 that are longer than the struts of the primary ring ofprevious embodiments. Furthermore, the secondary ring 538 is attached tothe primary ring 536 with connection strands 533 that extend from thebottom of the secondary ring 538 to the bottom of the struts 537 of theprimary ring. This differs from previously described embodiments whereinthe secondary ring 538 is connected to the top of the struts of theprimary ring 536. As a result, a higher percentage of the main expansionforce generated by the primary ring 536 is delivered through thesecondary ring 538. It also leads to the primary ring 536 extendingaxially beyond the secondary ring 538 whereas in previous embodiments,the primary ring is essentially below the secondary ring.

An advantage to this configuration is as follows. The larger surfacearea provided by the primary ring 536 leads to a greater dispersion ofthe expansion pressure (force per unit area) against the tissue by theprimary ring 536 and thus mitigates (or even eliminates) the tendency ofthe struts of the primary ring 536 to penetrate or migrate through thewall of the vessel tissue. At a minimum, this greater surface will slowdown the migration rate of the struts as compared to other embodimentsand as to the struts of the secondary ring 538. It does not, however,negatively affect the desired expansion pressure (force per unit area)of the secondary ring 538. Hence, a first advantage is that the primaryring 536 may better facilitate the anchoring properties of the device535 without degrading the scar inducing properties of the secondary ring538.

Another advantage of this configuration relates to how the scar inducingproperties of the device are executed by the device 535. If the struts537 of the primary ring 536 are prevented from migrating into the wallof the tissue, this will better ensure the proper migration of thestruts of the secondary ring 538. For example, if the struts of one sideof the secondary ring 538 migrate fully through the wall on one side ofthe vessel before similar migration by the struts on the other side ofthe secondary ring 538, the circumferential tension (caused by thevessel tissue) necessary for urging the oppositely sided struts tocontinue their migration will be released unless an independent force isexerted against these oppositely sided struts. This independent force isprovided by the struts 537 of the primary ring 536 as follows. Since thestruts 537 of the primary ring 536 have not migrated into the tissue (byvirtue of the larger surface area of these struts), they retain theirexpansion force. And because these struts 537 are independentlyconnected to the struts of the secondary ring 538, then the oppositelysided struts of the secondary ring 538 will continue to encounter theoutward expansion forces of the primary ring 536. As a result, uniformmigration of the struts of the secondary ring 538 into the surroundingtissue is substantially assured even if the migration of the entirecircumference of the secondary ring 538 does not occur simultaneously.In other words, by having the primary ring 536 serve essentially only asan anchoring ring (by virtue of its increased area), uniform outwardexpansion force is exerted against the struts of the secondary ring 538,regardless of when a portion of the secondary ring may migrate throughthe vessel tissue.

Referring to FIG. 25, a variation of the embodiment of FIGS. 24 and 24Amay include an electrical block device 520 wherein the struts 525 of theprimary ring 522 not only extend beyond the struts of the secondary ring524 but the struts 525 are configured to flare outwardly beyond thenormal diameter of the device 520. Configuring the struts 525 in thismatter allow the electrical block device 520 to better conform to thestructure of the ostium and pulmonary vein since typically the ostiumexpands outwardly as it merges with the atrial wall. This configurationmay cause the primary ring 522 to have even better anchoring propertiesthan the embodiment of FIGS. 24 and 24A.

Referring to FIGS. 26 and 27, another preferred embodiment for causingtissue scarring with an expandable ring is an electrical conductionblock device 530 that includes a series of small barbs 532 along thelength of each strut 531 of the device 530. These barbs 532 serve topierce the tissue wall of the vessel at the same time that the device530 is being expanded against the vessel wall. The barbs 532 createsmall cuts along the pressure path and thereby reduce the pressure(force per unit area) needed for each strut 531 to migrate through thevessel wall.

The barbs can be cut in the pattern shown in the flat sheet depiction ofthe device 530 in FIG. 27, wherein the barbs 532 lay flat, i.e., theylay circumferentially on the device instead of radially outwardly. Thebarbs 532 can then be bent into a radially outward position when thedevice is formed up to its final diameter. Typically this occursautomatically if the ratio of strut thickness to strut width isdecreased below about 1.0.

Furthermore, the embodiment depicted in FIGS. 26 and 27 can be usedalone, i.e., as the sole component of the electrical conduction blockdevice or it can be used in a two-ring or “two-cell” design as discussedpreviously. Referring to FIG. 27, the device 530 can serve as a primaryring as in previously described embodiments wherein a secondary ring canbe connected via the apertures that are located at one end of the struts531 of the device 530.

It is desirable to deploy the device in a very controlled and accurateway for all embodiments of the electrical block devices discussed inaccordance with the present invention. This includes the capability ofdeploying the device with a smooth release from the delivery device withno “jumping” of the position of the device in the target vessel. It alsoincludes the capability of repositioning the device or to remove thedevice if the physician is not pleased with the deployed position of thedevice.

One embodiment of such a delivery system useful particularly for theelectrical block devices described previously with respect to FIGS.13-27 is shown in FIGS. 28A-28C. FIG. 28A shows an electrical blockdevice 500 having a primary 504 and secondary ring 502 being deployedout of the end of the delivery catheter 700 into the ostium of apulmonary vein. This deployment is initiated by drawing back theexternal sheath 702 to allow the block device 500 to expand up towardsits formed diameter.

FIG. 28B shows the electrical block device 500 now fully expanded at thesite in the ostium of the pulmonary vein ostium. In this drawing it canbe seen that the electrical block device 500 is attached to the deliverycatheter 700 by an array of arms 539 projecting out from a hub 704 onthe inner shaft 705 of the delivery catheter 700. These arms 539 areconnected to the secondary ring 502 of the electrical block device 500.This array of arms 539 connected to the electrical block device 500allows the deployment of the device 500 to be controlled according tothe rate the outer sheath 702 is pulled back. In the partially deployedstate shown in FIG. 28A, the sheath 702 constrains the expansion of thearms 539 which then act to hold down the electrical block device 500.

This type of an assembly allows the device 500 to be deployed graduallyby controlling the rate that the sheath 702 is pulled back along thecatheter. This assembly also allows recovery or repositioning of theelectrical block device 500 if the physician so wishes by advancing thesheath 702 back over the arms 539 and the electrical block device 500.FIG. 28C shows the delivery catheter 700 being withdrawn away from thedeployed electrical block device 500 after releasing the connection ofthe arms 539 from the device 500.

FIGS. 29A-29C show a variation on delivery catheter design describedabove. In this embodiment the loops formed by the secondary ring 502 ofthe fully constrained electrical block device 500 shown in FIG. 16 areused to connect the electrical block device 500 to the delivery catheter700. These loops are hooked over a ring of pins 540 and are therebytrapped inside the sheath 702 of the delivery catheter 700 until thesheath 702 is withdrawn back beyond the ring of pins 540. FIG. 29B showshow this allows the primary ring 504 to be deployed while retainingconnection to the secondary ring 502 inside the end of the sheath 702.If satisfied with the location of the primary ring 504, the sheath 702is then withdrawn fully releasing the secondary ring 502 as shown inFIG. 29C.

FIG. 30 shows one embodiment in which the arms 539 are hollow tubeshaving a wire 708 running from the handle of the catheter 700, down theshaft of the catheter to the array of arms 539, then inside the arm andout the end. This wire 708 is then wrapped around the strut of ring 502and back into the arm 539. This wire 708 runs back down the arm to areleasable anchor point (not shown) in the catheter 700 shaft or back inthe handle (not shown). This connects the arm 539 to the strut 502.After the electrical block device 500 has been deployed, the device 500can be released by releasing the anchor point on the wire 708 andpulling the wire 708 out from the catheter handle as is shown in the farright view of FIG. 30.

FIG. 31 shows another embodiment of a connecting mechanism in accordancewith the invention. In this embodiment, the strut of the secondary ring502 has a notch 710 which provides a nest for a mating notched end ofthe arm 539. Arm 539 has a wire 708 running along it from the catheterhandle like that described with respect to FIG. 30. This wire 708 runsthrough holes 712 in the arm 539 on either side of the strut 502 forminga loop around the strut. The mating notches between the strut 502 andthe arm 539 act to absorb any axial load that may occur between thesetwo elements during delivery. The connection may be released afterdeployment of the electrical block device 500 by pulling the wire 708back through the holes 712 from the catheter handle as shown in rightviews of FIG. 31.

FIG. 32 shows another embodiment of a connecting mechanism in accordancewith the present invention. In this embodiment, the strut of thesecondary ring 502 has a small hole 714 cut in it. The end of the arm539 has a “U” shaped cradle 716 with holes 718 cut in each side of thecradle 716. The strut is placed in this “U” shaped cradle 716 duringassembly and a small pull wire 708 as described previously relative toFIGS. 30 and 32 is threaded through the holes 718 in the “U” shapedcradle 716 and the strut 502. After deployment of the electrical blockdevice 500, this connection can be released by pulling this wire 708back through these holes 714, 718 as shown in the right views of FIG.32.

FIG. 33 shows another embodiment of a connecting mechanism in accordancewith the present invention. In this embodiment, the strut of thesecondary ring 502 has a small hole 720. This hole 720 has a pair ofwires 722, 724 strung through it. One of these wires 722 has anincreased diameter 726 on its end that will fit through the hole 720when it is the only wire passing through the hole 720 but will not fitback through the hole 720 if the second wire 724 has been passed throughthe hole 720 after the increased diameter end 726 of the first wire 722has passed through the hole 720. In this way, the second wire 722 actsas a pin to “lock” the first wire 724 through the hole 720. This processcan be reversed as shown in FIG. 33 by withdrawing the second wire 724and then withdrawing the first wire 722 through the hole 720.

As mentioned earlier, the concepts disclosed relative to the previouslydiscussed connecting mechanisms could also be used to attach a deliverydevice to the electrical block device 500 at locations other than thestrut of the secondary ring 502 as shown above. For example, aconnecting mechanism such as is shown in FIG. 33 could also be wellsuited to a hole geometry such as that shown in FIG. 9. In this case thepairs of wires 722, 724 would extend radially out from the shaft of thecatheter 700 to pass through the holes in the blocking device. Thesewires could be radially extended or drawn back with a handle connectedto these wire pairs. In this way the wires could be used to control theradial expansion of the electrical block device 500 as was describedearlier, and be released from the electrical block device 500 whendesired by withdrawing the second wire and then the first wire as shownin FIG. 33.

Variably Expandable Electrical Block Device

Yet another preferred embodiment of the present invention illustrates avariably expandable electrical block device 600 and deployment apparatus616, illustrated in FIGS. 34-45. Generally, this device 600 functions ina manner similar to previously described embodiments by causing scarringat the ostium of the pulmonary veins. However, the structure of thevariably expandable electrical block device varies from previous designsin that it utilizes a non-continuous expandable ring 602 that allows forcompact loading and deployment.

FIG. 34 shows the non-continuous expandable ring 602 in its flattened,loaded position, while FIG. 35 shows the ring 602 in its natural coiledposition. The expandable ring 602 has two notable elements: anchoringbarbs 604 and ring wire holes 606. As the name implies, anchoring barbs604 provide anchoring support by penetrating the target tissue when theexpandable ring 602 is in its natural coiled position. This anchoringsupport prevents the expandable ring 602 from migration away from thetarget area while securing portions of the expandable ring 602 to theostium. Ring wire holes 606 are simply holes within expandable ring 602that allow a control wire 618 to pass through.

Referring to FIG. 36, the deployment device 616 is shown to have adeployment sheath 614 and a deployment catheter 612. The deploymentcatheter 612 is an elongated instrument that slides within deploymentsheath 614. Located on the end of deployment catheter 612 are controlarms 608, preferably made from nitinol, which serve to deploy theexpandable ring 602 at a target location as discussed in greater detailbelow. Control arm wire holes 610 can be seen at the ends of eachcontrol arm 608, allowing for control wires 618 to pass through each ofthe holes 610 and into a center channel (not shown) of the deploymentcatheter 612.

Referring to FIGS. 37 and 38, the present preferred embodiment uses twocontrol wires 618 for manipulating the expandable ring 602. Each controlwire 618 takes an overall looped path, extending out of and through thecenter channel in deployment catheter 612, through a control arm wirehole 610, into ring wire hole 606, across the diameter of the deployedexpandable ring 602, then through the opposite side's ring wire hole606, into an opposite control arm wire hole 610, and finally into thecenter channel in deployment catheter 612. Each control wire 618consequently crosses the diameter of expandable ring 602 such that thatwhen both control wires 618 are present, an “X” pattern spans thediameter of the expandable ring 602.

A user may tighten or loosen these two control wires 618 to manipulatethe size of the expandable ring 602. FIGS. 42 and 43 best illustratethis function, as the expandable ring 602 is shown in an expanded andcontracted position, respectively.

The control wires 618 also serve the secondary function of deflectingthe anchoring barbs 604 inward to prevent the sharp tips from beingexposed until the control wire 618 is withdrawn. This deflection can bebest seen in FIG. 39.

Referring to FIG. 40, the variably expanding electrical block device 600can be seen in a loaded state within the deployment sheath. As withprevious embodiments of the present invention, the expandable ring 602remains within the deployment sheath 614 until the end of the deploymentsheath reaches the target location of the pulmonary ostium. Note thatcontrol wires 618 are not shown for simplicity of illustration.

One of the inherent benefits of this design lies in its ability to passthrough significantly smaller diameter deployment sheaths for deliveryto the desired target site, while expanding to an appropriate diameter,similar to the previously disclosed embodiments of this application.

Preferably, the expandable ring 602 could be cut from a flat sheet ortubing made from nitinol, having a thickness of about 0.015 inches and aheight of about 0.070 inches. However, a variety of thicknesses andheights may be used so long as loading into a deployment sheath ispossible and proper expansion of the expandable ring 602 may beachieved.

This embodiment of the present invention may be operated by firstfinding the pulmonary ostium target area with the loaded deploymentapparatus 616 as depicted in FIG. 40. Referring to FIGS. 40 and 37, theuser pushes deployment catheter 612 within the deployment sheath 614,which, in turn, pushes expandable ring 602 out from the deploymentsheath 614. The user continues pushing the deployment catheter untilcontrol arms 608 are fully extended from the deployment sheath. Duringthis movement, the expandable ring 602 curls back on itself from itsstraight shape, forming its relaxed, circular ring shape. This resultsin the system having the configuration depicted in FIG. 37 in the leftatrium.

Referring to FIGS. 41, 42 and 43, the user is able to control thediameter of expandable ring 602 for purposes of matching the ring withthe target site by simply pulling on the control wires 618 to decreasethe diameter and/or releasing the wires to increase the diameter.Typically, a user will pull the control wires 618 to decrease theexpandable ring 602 diameter so as to allow the user to then easilyposition the ring 602 at the target position of the ostium.

In this regard, the control arms 608 are devised so as to havesufficient axial strength so that the user may use them to push theexpandable ring 602 forward. The user can track along a guide wire untileither the expandable ring 602 wedges into the ostium or until the ring602 is aligned with a predetermined axial marker of the desireddeployment position.

Referring to FIGS. 44 and 45, once the proper target position isachieved, the user releases the control wires 618 which then allow theexpandable ring 602 to increase in diameter, pushing against the targettissue. When the user is satisfied that the expandable ring 602 is inthe proper position, the final step of deployment is performed, namelyseparating the deployment apparatus 616 from the expandable ring 602. Todo this, a user must first remove control wires 618 from the expandablering 602 by pulling on one end of each control wire 618. Since only oneend of the control wire 618 is being pulled, the opposite end will bepulled through its path in the expandable ring 602 and out of thecontrol end of the deployment catheter 612. Each control wire 618 ispulled out of the electrical block device 600 in a similar manner.

When all of control wires 618 are pulled out, the anchoring barbs 604are free to bend outwardly from the expandable ring 602 and penetratethe target tissue. Additionally, the deployment apparatus 616 is free tobe retracted and removed from the patient, and the procedure may befinished, as best seen in FIGS. 44 and 45.

Optionally, additional anchoring devices may be used to help secure theelectrical block device. Typically, such devices include staples orsutures which are not integral parts of the ring but which are deliveredwith a separate device that can be tracked into position and fasten theexpandable ring to the tissue wall.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

1-9. (canceled)
 10. A method of treating an atrial arrhythmiacomprising: delivering an unexpanded implant to a target site in anostial region of a pulmonary vein; expanding said implant to an initialretention state wherein said implant substantially conforms to a wall insaid ostial region of said pulmonary vein; and, allowing said implant tocontinue to expand over time such that said implant migratessubstantially through said wall of said pulmonary vein, said migrationcausing a circumferential scar tissue response of said pulmonary veinthat treats said atrial arrhythmia.
 11. A method according to claim 10,wherein said implant ultimately migrates through the entire thickness ofsaid wall of said pulmonary vein.
 12. (canceled)
 13. A method accordingto claim 10, wherein the delivering of an unexpanded implant includesdelivering a compressed stent.
 14. A method according to claim 10,wherein the expanding of said implant includes expanding a spatialanchoring section of said implant.
 15. A method according to claim 14,wherein the allowing of said implant to continue to expand includesallowing a conduction block inducing section of said implant to expandinto said wall.
 16. A method according to claim 10, wherein theexpanding of said implant includes engaging retention surfaces in saidwall of said pulmonary vein.
 17. A method according to claim 16, whereinthe engaging of said retention surfaces includes engaging barbs on saidimplant in said wall of said pulmonary vein.
 18. A method according toclaim 10, wherein the delivering of an unexpanded implant includesdelivering an elongated implantable strip to said target site. 19-36.(canceled)
 37. A method of creating an electrical conduction block in apulmonary vein ostial region comprising: directing an implant towardssaid ostial region in said pulmonary vein; retaining said implant insaid pulmonary vein with a first component of said implant; causing theformation of circumferential scar tissue in said ostial region of saidpulmonary vein by allowing a second component of said implant to migrateinto said ostial region at a faster rate than said first component. 38.A method according to claim 37, wherein the causing of said scarformation includes causing said second component to migrate into ostialregion tissue.
 39. A method according to claim 37, wherein the retainingof said implant includes expanding said first component to a size thatcauses an expansion force on the internal walls of said pulmonary vein.40. (canceled)
 41. A method according to claim 37, wherein the retainingof said implant includes abutting the implant against a bifurcation ofsaid pulmonary vein. 42-48. (canceled)